Archive for July, 2010

Tales from the Nuclear Age:

SL-1 (part 3)

The SL-1 accident in January of 1961 was rather unique in the history of U.S. Nuclear Power. Even the later Three Mile Island event seemed to have much less consequence in the area of human life. Because this was the first serious scale U.S. accident since World War II with unconfined damage, there had been little planning for such an event. The NRTS safety planners had not quite envisioned such an occurrence, and so there was little pre-planning for the unique circumstances of this incident. This was, in the long view, an education for the entire nuclear industry. It was an education after the fact, but much was learned for future new planning and emergency procedures. No one had faced these unique circumstances before. The decisions and events confronted in these few days were to evolve into industry wide safety techniques, and new design wisdoms. For example, no reactor was ever again designed with only one main control rod for operation.

Let us return to the strange events of that first night. Relay teams of radiation workers have recovered the body of Army Private Jack Byrnes, which still shows movement and some signs of life on a stretcher. Air Force Trainee McKinley lay expired still inside. The whereabouts of Seabee Dick Legg is still unknown at the late hour.

As Byrnes is removed from the radiation field in the main building, he is found to still be highly radioactive. His body is undressed, on the assumption that the contamination is on the surface of the clothes. But even after the clothes are removed and buried, there is still a dangerously high local radiation field around the body; too high for personnel to be near for more than a few minutes. The man’s body seemingly has been penetrated with radioactive particles and debris, suggesting some sort of explosive event. At first a chemical explosion is suspected.

Byrnes is put into an ambulance and driven towards the main road, to meet the NRTS night nurse, Hazel Leisen, who valiantly enters the vehicle to administer care. At 11 p.m. Byrnes breathes his last, and she is unable to resuscitate him. The Assistant Medical Director enters and pronounces the man is dead.

The local medical facility is unequipped to handle a highly radioactive corpse. There is literally no place to put him. Radiation levels nearby are over 500 r/hour. All personnel abandon the vehicle. The now lifeless body remains inside, and the ambulance is closed up. The driver heads the vehicle out into the desert sands, and as the vehicle speeds up the driver jumps out from the driver’s seat allowing the ambulance to proceed unmanned into the seventeen degree below zero desert night . It is hoped the contamination will decay to approachable levels within a short time.*

Since the third man (Navy Electrician’s Mate Richard Legg) has presumably expired in a high radiation field, work is now slowed to accommodate safety of the rescue crews. On the evening of January 4th the second body (McKinley) is removed by one-minute teams. It is necessary to discover what had exactly happened, and radioactive Gold from McKinley’s watch band is removed, along with a small Copper screw from his cigarette lighter. These are examined and the presence of new isotopes show evidence that a nuclear excursion of the reactor core emitted a sudden burst of neutrons. It remains to determine what has caused this strange event.

As more crews dash in they recount massive observed damage inside the building. Finally someone looks up to observe a stunning sight. The main control rod is observed to be stuck into the ceiling of the building, nine feet above the reactor core where it should have rested. With amazing force the control rod had passed through the body of the third man working on the top of the reactor, and Legg’s body was now seen to be stuck to the ceiling of the reactor building, pinned and impaled there by the reactor control rod which had passed through his corpse!

Radiation levels were prohibitive for several more days . On January 9th, four relay teams of two men each were allotted 65 seconds exposure times. A new dangerous situation now existed. If any pieces of the body should fall down into the reactor core, it could initiate a reactor criticality event. A crane was carefully moved in and metal shields installed to isolate the operators cab from the radiation. The body was finally removed by means of a net arrangement. Forensic examination revealed some body parts were highly radioactive. These parts were wrapped in lead foil before the bodies were turned over to the respective services for shipping to locations specified by the families. A health physicist accompanied the shipment of each cadaver. The bodies were buried in lead lined caskets and encased in cement. Air Force Specialist McKinley is buried in Arlington National Cemetery.

Retrieval and disposal of the bodies finally ended what was termed to be “Phase One” of the SL-1 investigation. Subsequent examination of long scratches on the side of the control rod and guide tube seemed to indicate it had been withdrawn to a distance of 26 inches instead of the specified 4 inches. This added to the mystery of this strange event, and opened a whole series of new possible incidents leading to the catastrophic climax. Phase Two is begun to stabalize and clean up the reactor, and methodically examine the clues left behind to uncover how this bizarre sequence of events had occurred …

(to be continued …)

*In a later account, Dr. George Voelz, NRTS Medical Director, relates a somewhat different set of events. He says that “…Around 6:30 a.m. the ambulance drove to the Chem Plant into a large enclosed receiving bay…[near a] decontamination room lined with stainless steel…”

SL-1 (part 2)

The Army Stationary Low Power Nuclear Reactor number 1 (SL-1) had been safely generating electricity since 1958 in a remote part of the Idaho Reactor Testing Station (IRTS). On the night of January 3rd, 1961, three men were working on top of the reactor core. The reactor had been shut down before Christmas for annual maintenance, and the water level in the reactor had been lowered two feet to expose the top of the core. The SL-1 had a unique design. It operated with only one main control rod, located in the center of the core. Approaching 9 p.m., it was the task of the three night crewmen to lift up this main control rod and reattach it to its control rod drive mechanism above the core.

This required Army private Jack Byrnes to physically lift the main rod three inches out of the core, so it could mate with the controller above for reattachment. This was a safe movement distance used several times before; not enough to initiate a chain reaction. Private Byrnes’ wife had called him on the telephone at work about 7 p.m. that evening, to tell him their marriage was ended and she wanted a divorce. She told him not to come home, ever.

At 9:01 p.m. that evening the IRTS fire alarm system alerted the main fire station that there was a fire at the SL-1 reactor. Fireman soon arrived in the 17 degrees below zero weather, to find no sign of the evening work crew. The place seemed deserted, no fire was evident but radiation alarms were sounding throughout the facility building. Upon entering the adjacent control room it was observed to be empty, but three lunch pails were seen lined up on a table awaiting their owners. When personnel crossed the yard and approached the reactor building, their low range radiation meters went off scale. The fire crew quickly retreated back to safer ground and called for assistance.

Sixteen minutes later a Health Physics technician arrived. He carried a higher range meter and, together with a fireman, both wearing full body coveralls and Scott Air Paks again approached the stairs. The Air Pak has a backpack Oxygen tank and hose to a facemask. It keeps a positive pressure inside the face mask in case of a leak. The mask was to prevent inhaling fission products. (Note: There is no “suit” which protects against gamma radiation, short of a suit of lead armor which would be far too heavy to allow walking around.) Mounting the stairs again with a fireman, the HP’s meter registered a dose rate of 25 Röntgens per hour. Again they beat a hasty retreat.

To put this in perspective, we live in a radioactive world. Cosmic rays from space, radioactive decay products in the air all give us a natural background radiation exposure. Many with below ground basements have small amounts of Radon gas decaying in the basement air. Even eating a banana gives our bodies a tiny dose from Potassium 40. (Truckloads of bananas crossing the border from South America often set off the border radiation detectors due to the radiation from banana Potassium.) So the ordinary population in the United States receives a radiation dose which averages 0.36 Röntgens per year. Current international standards (in 2010) allow radiation workers in the commercial industry to accumulate a maximum annual dose of five Röntgens. (Army personnel fall under different Army regulations. ) So the SL-1 rescue workers, in a radiation field of 25 R/hour would receive the maximum permissible annual dose in about 12 minutes of whole body exposure. This would require them to retire immediately and not work with radioactive materials for the rest of the year. In the worst case emergency, a short term whole body radiation dose of 450 Röntgens is sufficient to kill 50 percent of those persons exposed.

By this time, a search of the peripheral buildings determines there are no workers anywhere else on the site. It’s concluded the three missing crew members must be located in the main Reactor building, evidently in a high radiation field.

A few minutes later two HP techs arrive in full coveralls bearing very high range meters, capable of sensing 500 R/hr. Two firemen and the HP ascend the stairs watching the meter. At the top of the stairs they can see serious damage on the top of the core inside and no personnel. There the meter records a dose rate higher than 500 R per hour, a lethal dose rate. The Health Physics in charge orders all to withdraw. Meanwhile the Combustion Engineering and Idaho authorities are notified.

John Horan, Director of Health and Safety leaves his home in Idaho Falls for his office where he takes charge of the situation via radio to the NRTS. A “Class One” Emergency (local and isolated) is declared. Medical personnel, higher authorities, local police and fire units, the Atomic Energy Commission Headquarters are all alerted. The Radiological Assistance Plan is activated, alerting still more area complexes. Local highways and local desert sagebrush are monitored for contamination, in case a cloud of radiation has escaped. Civil aircraft are notified to begin aerial site radiation surveys.

Two supervisor personnel and HP devise a plan which has become rather standard in high radiation events. Personnel would be allowed to run into the radiation field, do a small amount of work and retreat quickly, to be followed by another crewman who does a little more work etc. Each run time is calculated to give only a small dose over a very short period. The worker is accompanied by a HP who’s job is simply to watch a stop watch and signal retreat when the time limit has been reached. In this high radiation field, dwell times are limited to one to two minutes, including the run in and exit times. Each person wears a small Dosimeter resembling a pencil which clips on a pocket. It will record the accumulated dose when the worker leaves the field. The dose (by law) is recorded in the employer’s records, which are periodically inspected to verify accumulated doses are within legal limits.

Using this method, the allowed time is one minute. Two military and a HP race up the stairs. Entering the second floor, they see two bodies, one badly mutilated and one moving slightly. There is no sign of the third man. The equipment in the room is a shambles, as is the top of the reactor core. The radiation field inside the door is 1,000 R/hr. They quickly exit. On the next relay five men race in with a stretcher to recover the moving body. The floor is covered with inches of water which was inside the reactor core. Scattered under the water are the round shielding steel pellets which cause them to slip and slide in the radioactive water. While the (moving) body is put on the stretcher, two others check the second body and determine he is probably dead. There is no sign of the third man …